Leads implanted in or about the heart have been used to reverse certain life threatening arrhythmias, or to stimulate contraction of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing pulses to the atrium or ventricle. Technically, the pacemaker or the automatic implantable cardioverter defibrillator (AICD) receives signals from the lead and interprets them. In response to these signals the pacemaker can pace or not pace. The AICD can pace, not pace or shock, and not shock. In response to a sensed bradycardia or tachycardia condition, a pulse generator produces pacing or defibrillation pulses to correct the condition. The same lead used to sense the condition is sometimes also used in the process of delivering a corrective pulse or signal from the pulse generator of the pacemaker.
Cardiac pacing may be performed by the transvenous method or by leads implanted directly onto the ventricular epicardium. Most commonly, permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. The lead may also be positioned in both chambers, depending on the lead, as when a lead passes through the atrium to the ventricle. sense electrodes may be positioned within the atrium or the ventricle of the heart. For pacing applications, the lead may be positioned in cardiac veins or arteries.
Positioning an electrode disposed on a distal end of a lead within a vein or artery presents additional challenges in maintaining the lead in a fixed position since the distal end of the lead does not abut a surface. These challenges also may result in poor pacing and sensing capabilities of the electrode.
Therefore, there is a need for a lead having an electrode for positioning within cardiac veins, or arteries that allows for fixation therein. In addition, what is needed is a lead which provides desirable pacing and sensing properties.